Method of purifying and desulphurizing motor fuel



Patented Apr. 26, 1938 PATENT OFF-ICE METHOD OF PUBIFYING AND DESULPHUR- IZING MOTOR FUEL Hans Brooke and Hellmuth Schmitz,

Y Essen, Germany No Drawing. Application July 3, 1934, Serial No. 733,606

5 Claims.

This invention refers to a method of desulphurizing motor fuel, particularly hydrocarbons destined to be used and burnt in stationary or vehicle motors.

The invention especially refers to a method of desuiphurizing such fuel, as benzol, benzine natural or cracked, and other derivatives of petroleum be found any more in the motor fuel.

It is another object of the invention-to stabilize the motor fuel so that it is not subject to any changes during storage.

It is another object of the invention to deodorize motor fuel as far as the odor is due to its sulphur content.

It is another purpose of the invention to desulphurizev motor fuel by a highly efllcient method keeping down losses of the fuel due to the treatment to the smallest possible amount.

It is another object of the invention to de sulphurize motor fuel by simple and eflicient means at the lowest possible cost.

According to the invention, the motor fuel is gently treated with diluted sulphuric acid and afterwards treated at elevated temperature and under elevated pressure in the presence of alkali hydroxides, or alkaline earth hydroxides. Especially aqueous alkaline solutions are useable as for instanceysodium hydrate, solutions of caustic potash, and the like.

By such treatment the entire content in the motor fuel of sulphur can be exceedingly reduced and, if necessary, the sulphur almost completely removed.

In standard motor fuel, a sulphur content only of less than about .4% is to 'be allowed. By using a method according to this invention, the originally higher sulphur content of the fuel can easily be reduced below the limit of about .4%, to about .l% and below.

The inventors do not intend to limit the invention to any scientific explanation. They believe, however,that by the method according to the invention, in the first place the carbon disulphide and all the other sulphur being combined in a similar way as carbon disulphide, are completely removed. Among these sulphur combinations,

tosuch an extent that practically no sulphur can other organic sulphur, as for instance mercaptans, are comprised.

As is well known to the'art, carbon disulphide and similar organic combinations of sulphur cannot be removed by washing the fuel with sulphuric acid, as such sulphur combinations are throughout stable against sulphuric acid. The method according to this invention, however, achieves the surprising results that the carbon disulphide and other similar combinations of sulphur, including mercaptans, are completely removed.

In case that the sulphur content in the raw material is extremely high and that the sulphur not only is present in the form of carbon disulphide but also in that of other combinations, particularly organic combinations, and for ill-m stance in the form of thiophanes, then, according to the invention, such fuel is first subjected to washing with sulphuric acid of low concentration and, subsequently, the fuel. so treated is subjected to a treatment under elevated pressure in the presence of alkali hydroxides. By washing the fuel with acid, obviously those combinations of sulphur are attacked first which, as for instance thiophanes and the like, are not capable of being removed by alkaline refining alone, but are to be sulphurized and polymerized first and then removed in this form. Any balance of sulphur, or

combinations thereof, remaining in the fuel, not

being attacked, or washed out, by the acid, can then be removed quite easily by a treatment with alkali hydroxides, so that finally the entire sulphur content is either removed from the fuel or, at least, reduced to an amount sufiicient for practical purposes.

Taking as example a raw benzol usable as a motor fuel, containing approximately 1.25% of sulphur, the sulphur content can be reduced to about 1% by treating such liquid fuel with a diluted sulphuric acid of about B. As known in the art, by such cautious treatment with diluted sulphuric acid, all constituents of the fuel capable of forming resins, are either destroyed, or changed, or removed. By treating the fuel subsequently at elevated temperature, and under elevated pressure, in the presence of alkali hydroxides or alkaline earth hydroxides, or both, the sulphur content iii this fuel can easily be reduced to about 3%. It is possible, therefore, as investigations by the inventors have proven, by using the method according to the invention, to refine the fuel under treatment and to reduce its content of sulphur below the normal limit of .4% also in cases where the raw material contains an exceedingly large amount of sulphur.

It is to be understood that the method according to the invention can be applied both to a raw material not yet refined in one of the usual ways,'or to materials which had previously been subjected to one of the known usual refining or purifying processes, with the result, however,

that more than about .4% sulphur, or combinations of it, still remained in the material or, even if less than that remained, a further reduction or the entire removal of the sulphur was desired. Furthermore, the method according to the invention is usable for any kind of liquid fuel to be burnt in combustion engines of any kind, including the highand low-boiling fuels as gasoline, petrol, benzol, benzine, and spirits which may also be mixed as the case may be, and which may be produced either by distillation of coals of any kind the distillation product afterwards being fractionated, if necessary, or which may be derived from natural oils like petroleum, directly or by cracking, or by some other suitable treatment.

As a second example of the application of the method, according to the invention, a raw fuel may be taken which had not been refined bya treatment with concentrated or diluted acid, but which is intended to be stabilized for storage by means of inhibitors. I

It is known to the art that such inhibitors can be added to such fuel with optimal effect and in optimal amounts only in case that the phenols ordinarily present in such highor low-boiling oils, are removed before the addition of the inhibitors. If some inhibitors have been added before removing the phenols, the balance of the inhibitors is to be added after removal of the phenols. If the raw oils (fuels) are treated, howover, according to the invention, under elevated pressure and at elevated temperature in the presence of alkali hydroxides, or alkaline earth hydroxides, the sulphur content is reduced and the phenols are simultaneously completely removed, so that the material is ready for the addition of the optimal amount of inhibitors. In other words, two effects are achieved simultaneously by the method of the invention. By one of the inventors it had previously been suggested to subject the fuel to refining by treating it with diluted sulphuric acid of about 60 B. and to remove the esters and the sulfo-acid produced by this treatment by. means of subsequent treatment of the fuel with hot sodium hydrate. If, therefore, a material as for instance benzol, or benzines, or mixtures thereof, which had been refined previously, by a treatment with diluted sulphuric acid, is subjected to a further treatment according to the invention at elevated temperature above about IOU-120 and, sometimes, 130-150 C., and at elevated pressure such as, for instance, naturally occurs if the material is being heated in a closed still to a temperature in the range of about 100-150" C. and more, the sulphur content of the material will be substantially reduced and the'esters, sulphur-acids, and other constituents, causing a decolorization or a resin-formation or other phenomena of unstabllity, will be destroyed and a high degree of stability during storage will be secured. If the temperature of the liquid fuel material contained in the closed vessel is raised to about 90 C. a pressure between about 2.5 and 3 atmospheres per sq. cm. results; if the temperature is further raised up to about 130 C. the pressure is increased to about 7.5 to 8 atmospheres, and if the temperav vantages of decisive importance.

ture is elevated to about 150 C. the pressure resulting in the vessel amounts to about 15 atmospheres.

The invention, therefore, presents several ad- The invention permits to remove the sulphur from the fuel to a very high extent or even altogether. Furthermore, by the treatment according to the invention, the material can be freed from sulphur and simultaneously be prepared to receive the optimal amount of inhibitors. If purifying the fuel by a treatment according to the invention, the sulphur content will be substantially reduced and-simultaneously, constituents of the fuel will be destroyedwhich otherwise are the cause of unstability.

Taking as a third example a fuel with a sulphur content of about 115% or more, a purification was advisable according to the prior art by treating the material with concentrated sulphuric acid of about 66 B.

As known: to the art, however, by such treatment losses of material may occur. In such case, according to the invention, the material will first be fractionated by distillation in such way that a fraction is obtained with higher sulphur content and. another one with lower sulphur content. Regularly the fractions boiling between about 78-90 and 100 C. contain more sulphur while the higher-boiling fractions of the fuel, boiling up to about 250 C. and more, have a lower sulphur content. The lower boiling fraction with the higher sulphur content may be treated in the known way with concentrated sulphuric acid of about 66 B. to remove a substantial part of the sulphur and to destroy chemical compounds of it like the thiophanes, while the higher-boiling fractions may be treated according to the invention with diluted sulphuric acid of about 60 B. In such way, the losses during washing with acid are reduced as far as possible, namely so far as the higher-boiling fractions are concerned.

For the sake of clearness it may be stated that a high sulphur content means in this case one that cannot be removed successfully by subsequent treatment, according to the invention, if the material had not been previously treated with concentrated sulphuric acid. Such sulphur content regularly amounts to more than approximately 1.25%.

It is to be understood that the invention is not limited in any way to the examples cited and to the temperatures and pressures mentioned. But they may be adjusted with a view to the fuel to be treated and its sulphur content, and the general rules given in the specification and the appended claims.

What we claim is:

1. In a method of desulphurizing a liquid motor fuel consisting essentially of hydrocarbons obtained by coking solid carbonizable fuel material and containing sulphur and substantially organic compounds thereof in amounts exceeding about 0.5%: treating the fuel with diluted sulphuric acid of about 60 Baum at ordinary temperature and thereupon subjecting it to heat treatment in a closed vessel in the presence of a reagent selected from a group consisting of alkali hydroxides and alkaline earth hydroxides within a temperature range of about 90 C. to about 150 C. and under elevated pressure as developing in said vessel at thus raised temperature until the amount of said sulphur and its compounds is reduced to substantially below 0.4%.

2. In a method of desulphurizlng a liquid motor fuel consisting essentially of hydrocarbons ob tained by coking solid carbonizable fuel material and containing sulphur and substantially organic compounds thereof in amounts exceeding about 0.5% treating the fuel with diluted sulphuric acid of about Baum at ordinary temperature and thereupon subjecting it to heat treatment in a closed vessel in the presence of a reagent selected from a group consisting of alkali hydroxide and alkaline earth hydroxides within a temperature range of about C. to about C. and under elevated pressure as developing in said vessel at thus raised temperature until the amount of said sulphur and its compounds is reduced substantially below 0.3%.

3. In a method of desulphurizing a liquid'motor fuel consisting essentially in benzol and containing sulphur and substantially organic compounds thereof in amounts exceeding about 0.5%: treating the fuel with diluted sulphuric acid of about 60 Baum at ordinary temperature and thereupon subjecting it to heat treatment in a closed vessel in the presence of a reagent selected from a group consisting of alkali hydroxides and alkaline earth hydroxides within a temperature range of about 90 C. to about 150 C. and under elevated pressure as developing in said vessel at thus raised temperature until the amount of said sulphur and its compounds is reduced substantially below 0.4%.

4. In a method of desulphurizing a liquid motor fuel consisting essentially of benzine and containing sulphur and substantially organic compounds thereof in amounts exceeding about 0.5%: treating the fuel with diluted sulphuric acid of about 60 Baum at ordinary temperature and thereupon subjecting it to heat treatment in a closed vessel in the presence of a reagent selected from a group consisting of alkali hydroxides and alkaline earth hydroxides within a temperature range of about 90 C. to about 150 C; and under elevated pressure as developing in said vessel at thus raised temperature until'the amount of said sulphur and its compounds is reduced to substantially below 0.4%. a

5. In a method of desulphurizing liquid motor fuel obtained by coking solid carbonizable fuel material consistingv essentially in a mixture of hydrocarbons boiling between about'IB" and about 250 C. and containing more than about 1.25% admixtures consisting of sulphur and compounds thereof: the steps of fractionating said mixture into a higher boiling part having a lower content of about 0.5 to 1.25% said admixtures, and a lower boiling part having a higher content of sulphuric admixtures; treating said higher boiling part with diluted sulphuric acid of about 60 Baum at ordinary temperature and thereupon subjecting it to heat treatmentina closed vessel in the presence of a reagent selected from a group consisting of alkali hydroxides and alkaline earth hydroxides within a temperature range of about 90 to 150 C. and under elevated pressure as developing in said vessel at thus raised temperatures until the amount ofsaid admixtures is reduced substantially below 0.4%.

HANS BROCHE.

HELLMUTH SCHMI'IZ. 

